The present invention relates to an intravascular imaging method and apparatus which allow the acquisition of endoscopic images of small internal cavities of the body including methods and apparats for visualization through opaque liquid media.
Heart and blood vessel diseases are among the main causes for morbidity and mortality in Western society. Therefore, interventional procedures involving blood vessels of the heart are among the most widely used in the medical field. The pathology that is in the base of most acute coronary syndromes and sudden cardiac deaths is atherosclerosis. In is process, atherosclerotic plaques, which are an active collection of different cells, mainly immune cells and smooth muscle cells along with deposits of fatty substances, cholesterol, cellular waste products, calcium and other substances, are accumulated in the inner lining of an artery. Stable plaques, which cause the more significant narrowing of the arterial wall, are considered the major factor in the development of angina pectoris (chest pain). However, studies from recent years have shown, that unstable angina, myocardial infarctions (heart attacks) and sudden cardiac related deaths are caused mainly by unstable plaques, other known as vulnerable plaques. This type of plaque is usually smaller and therefore less significant and difficult to detect with currently used angiographic methods described hereafter.
Some of the important developments were made in the field of minimally invasive procedures. A very common diagnostic and therapeutic procedure is cardiac catheterization. The commonly applied method, angiography, includes imaging the heart and coronary blood vessels using an X-ray camera as the imaging device, and a catheter, through which a contrast substance is injected into the heart and vessels to enable them to be viewed by the camera. This method gives a two-dimensional monochromatic view of the heart and blood vessels as viewed from the outside. This method detects major occlusions by identifying places where blood flow is disturbed and it may direct the PTCA (Percutaneous Transluminal Coronary Angioplasty) or stent-inserting technique to the place of the occlusion, but it does not give a direct view of the occlusion site or the surrounding area. One of the major risks of the techniques described above is a rupture or a disruption in the fibrous cap covering the plaque and the release of plaque particles into the blood steam. These particles may cause numerous small occlusions in the coronary arteries but also may cause occlusions in small blood vessels of other organs, such as the brain kidney, or lungs. A direct, clear view of the field of operation, as provided in the current invention, could substantially decrease the risk of disruption, as described above. Also, and perhaps more importantly, only through intra-vascular imaging will it be possible to detect the smaller, vulnerable plaques. The effectiveness and precision of the plaque treatment, when assisted with direct intra-vascular imaging such as in the present invention, would be enhanced when compared to current indirect imaging methods.
Important methods that have been developed to confront the issue of intra-vascular imaging are angioscopy and intra-luminal ultrasound. New techniques, which are still under development, include Optical Coherence Tomography (OCT) and infrared endoscopy.
Angioscopy is a form of endoscopy developed for the arteries. Because the illumination used in angioscopy is in the visible wavelength range, in which the blood that fills the arteries is opaque, the method requires a way of moving the blood from the field of view prior to visualization. One way to do this is by injecting a high-pressure physiological fluid into the vessel to temporarily displace the blood, as disclosed in patents U.S. Pat. Nos. 4,827,907, 4,998,972, 5,730,731, 5,010,875 and 4,934,339. Another way of clearing the field of view is by inflating a balloon, which is positioned at the distal end of the angioscope, in front of the camera-head or optical assembly. The balloon is made of a transparent substance, so that when it is inflated inside the blood vessel, with either gas or a transparent liquid, it pushes the blood away from the distal end of the angioscope and clears a field of view of the walls of the vessel. Such an apparatus is described in U.S. Pat. Nos. 4,784,133 and 5,411,016; the latter patent disclosing a transparent part at the distal end of the angioscope in addition to the balloon surrounding it. A similar apparatus is disclosed in U.S. Pat. No. 4,470,407, except that the optical system terminates inside the balloon (also allowing laser operation through the balloon). An apparatus that uses two spaced and expendable balloons, that occlude and isolate an operating area in the blood vessel between them, is disclosed in U.S. Pat. No. 4,445,892. Most methods combine an inflatable balloon with injection of a transparent liquid. The balloon coaxially surrounds the sheath at the distal end of the catheter and, when inflated, it blocks some of the blood flow. The method described above allows the injection of less flush liquid and at a lower pressure, which is safer and more efficient. Prior art in which the method described above is used is U.S. Pat. Nos. 4,576,145, 4,576,146, 5,263,928 and 5,464,394. A combination of an angioplasty balloon with intra-vascular endoscopy is disclosed in patents EP177124A, U.S. Pat. Nos. 5,116,317 and 4,961,738. In the latter patent, the optical system terminates within the balloon and there is a xe2x80x9cworking wellxe2x80x9d in the balloon to allow the insertion of instruments into the lumen of the vessel.
Another method for intra-vascular imaging is the use of ultrasound. The ultrasound transducer is positioned at the distal end of a catheter inside the blood vessel and the ultrasound transducer is used to obtain an image of the lumen and walls of the arty. Patents referring to this kind of apparatus are U.S. Pat. Nos. 6,129,672, 6,099,475, 6,039,693, 6,059,731, 5,022,399, 4,587,972, 4,794,931, 4,917,097 and 5,486,170. A patent that combines PTCA with ultrasonic imaging is U.S. Pat. No. 5,167,233.
OCT provides a three-dimensional image by performing optical measurements, and it can be used in intra-vascular imaging. Related patents are U.S. Pat. Nos. 6,134,003, 6,010,449, and 5,459,570.
The opaqueness of blood at visible light wavelengths poses a specific problem when attempting to acquire an image of an intra-vascular space. One solution to the problem noted above is to utilize infrared (IR) light to enable visibility through the suspended particles and cells in the blood. A patent that discloses a method for using deep-IR light for imaging through blood is U.S. Pat. No. 6,178,346. The use of deep-IR wavelengths to achieve visibility in a blood medium as described in the referred patent requires very high-energy illumination, which has risks and disadvantages when used inside the body. The use of near-IR radiation substantially diminishes risks. U.S. Pat. No. 4,953,539 discusses the use of an endoscopic device, which is illuminated from outside the body with infrared light. The referred patent serves as an example of the use of infrared light in imaging body organs. External illumination has not been used to date for intra-vascular imaging.
A well-known property of human tissue is that it has different absorption, scattering, and attenuation coefficients of IR radiation. This fact allows different types of tissues to be distinguish in general, and allows different types of plaque to be to be distinguished in particular. Reference is made to xe2x80x9cA Review of the Optical Properties of Biological Tissuesxe2x80x9d Cheong, Prahl and Welch, IEEE J. of Quantum Electronics, Vol 26 No 12 December 1990.
According to a first aspect of the present invention there is thus provided an invasive imaging apparatus comprising;
a. A flexible catheter with a proximal end and a distal end, said distal end being shaped for insertion into a blood vessel along a guide wire thereby to reach remote places in the vasculature or other organs.
b. An optical assembly positioned at the distal end of said catheter comprising an image sensor positioned non-perpendicularly to the longitudinal axis of said catheter.
c. At least one illumination source for illuminating an immediate region beyond the distal end of said catheter.
d. At least one working channel running from the proximal to the distal end of said catheter.
Preferably said illumination source utilizes at least one wavelength taken from within a range comprising visible light, near infra-red, and infra-red light.
A preferred embodiment comprises a plurality of illumination sources an said illumination sources are controlled together.
A preferred embodiment comprises a plurality of illumination sources and said illumination on sources are controlled separately.
Preferably said illumination source uses at least one wavelength preselected to improve visibility through blood.
Preferably said illumination source is comprised of an infra-red illumination source positionable outside of said patient""s body.
Preferably said illumination source is controllable to be aimed directly at an imaged object from the direction of said imaging assembly.
Preferably said illumination source is controllable to be directed in a general viewing direction.
Preferably said optical assembly comprises optical components and an imaging assembly.
Preferably said imaging assembly comprises said image sensor and an illumination sensor.
Preferably said optical components comprise a lens With two optical planes, a shutter, and a light deflector.
Preferably sad light deflector is one of a prism and a mirror with a reflecting surface.
Preferably said sensor and said illumination sensor are operable to sense at least one wavelength taken from within a range from visible light to infra-red light to correspond to said illumination source.
Preferably a polarized filter is positionable before at least one of a member of a group comprising said illumination sensor, said image sensor, said illumination sources, and said lens, and said polarized fiber polarization direction is controllable to enhance image quality.
A preferred embodiment comprises a central control and display unit connectable to the proximal end of said catheter from outside of the patient""s body.
Preferably said working channel comprises a guide wire.
Preferably said working channel is usable for controllably passing through fluid to said distal end of catheter.
Preferably said image sensor is positioned substantially parallel to the longitudinal axis of said catheter.
Preferably said image sensor is shaped to fit within restricted dimensions of said catheter.
Preferably said image sensor is a CMOS or CCD-based pixel sensor.
Preferably said image sensor comprises an aging area shaped in a rectangular pixel array.
Preferably said rectangular pixel array measures 128xc3x97256 pixels.
Preferably said sensor comprises sensor control electronic circuitry located beneath a shorter side of said imaging area, said imaging area being arranged as a rectangular pixel array.
Preferably I/O and supply pads for said electronic circuitry are placed along at least one of the shorter sides of said image sensor.
A preferred embodiment with a local controller located at the distal end of said catheter to coordinate data flow to and from said optical assembly and to perform commands received from said central control and display unit.
Preferably said display and cool unit is operable to control the timing and amount of injection of said fluid.
Preferably a transparent balloon-like structure is positioned at said distal end of said catheter to displace blood from around the optical sensor-head, allowing clear visibility.
Preferably said balloon-like structure is rigid.
Preferably said balloon-like structure is flexible.
Preferably said balloon-like structure is inflated and deflated by means of using a liquid or a gas passed through said working channel.
Preferably said optical assembly comprises two image sensors for obtaining a stereoscopic image.
Preferably the injection of said fluid is synchronized with the operation of said optical assembly, synchronizing said operation and said injection with the cycle of patient physiological conditions.
Preferably one of said physiological conditions is heart beat sensible using a heart rate sensor (such as a plethysmograph, or other device) connectable to a patient""s body from outside of said patient""s body or insertable into said blood vessel through said catheter.
Preferably information from said heart rate sensor is transferred to said central control unit enabling synchronization with said physiological conditions.
Preferably said balloon-like structure is pressure-sensed to provide real-time feedback when said balloon-like structure impinges upon an obstacle, such as a blood vessel wall.
Preferably said working channel is usable for passage of therapeutic instruments to a site of operation.
Preferably said optical assembly is used in conjunction with a laser cutting device to enable laser operated surgery.
Preferably said laser cutting device is used to obtain biopsy biological samples by cutting and transfer through said working channel to the proximal end of said catheter.
Preferably said optical assembly and said laser cutting device are used in conjunction with one of a suction and nano-gripper mechanisms to enable visual inspection of a desired location for biological sample retrieval.
According to a second aspect of the present invention there is provided an invasive imaging control apparatus comprising:
a. A flexible catheter with a proximal end and a distal end, said distal end being shaped for insertion into a blood vessel along a guide wire thereby to reach remote places in the vasculature or other organs.
b. An optical assembly positioned at the distal end of said catheter.
c. At least one working channel running from the proximal to the distal end of said catheter.
d. A control unit for regulating the opacity level of blood in said blood vessel around sad distal end of said catheter, controllably injecting quantities of fluid into said blood vessel in the vicinity of said optical assembly, thereby enhancing visibility.
Preferably said optical assembly comprises an illumination sensor operable to sense at least one wavelength taken from within a range from visible light to infra-red light.
Preferably said working channel is usable for controllably passing through fluid to said distal end of catheter.
Preferably said control unit is connectable to the proximal end of said catheter from outside of the patient""s body.
Preferably said control unit is operable to control the timing and amount of injection of said fluid.
Preferably the injection of said fluid is synchronized with the operation of said optical assembly, synchronizing said operation and said injection with the cycle of patient physiological conditions.
Preferably said fluid is insertable into the immediate region of said distal end of said catheter to change the optical characteristics of blood in said immediate region.
Preferably said fluid comprises one or more fluids selected to modify the optical characteristics of blood plasma to render said optical characteristics to be as close as possible to those of red blood cells.
Preferably said physiological condition is heart beat sensible using a heart rate sensor (such as a plethysmograph, or other device) connectable to a patient""s body from outside of said patient""s body or insertable into said blood vessel through said catheter.
Preferably information from said heart rate sensor is transferred to said central control unit enabling synchronization with said physiological conditions.
According to a third aspect of the present invention there is provided an invasive imaging control apparatus comprising:
a. A flexible catheter with a proximal end and a distal end, said distal end being shaped for insertion into a blood vessel along a guide wire thereby to reach remote places in the vasculature or other organs.
b. An optical assembly positioned at the distal end of said catheter.
c. At least one working channel from the proximal to the distal end of said catheter
d. A semi-permeable membrane positioned at said distal end of said catheter, surrounding said optical assembly extendable to displace blood from around the optical assembly allowing clear visibility.
Preferably said membrane is rigid.
Alternatively, said membrane is flexible.
Preferably said membrane is inflated and deflated by means of controllably passing a fluid through said working channel to said distal end of catheter.
A preferred embodiment has a control unit connectable to the proximal end of said catheter from outside of the patient""s body.
Preferably the injection of said fluid is synchronized with the operation of said optical assembly, synchronizing said operation and said injection with the cycle of patient physiological conditions.
Preferably one of said physiological conditions is heart beat sensible using a heart rate sensor (such as a plethysmograph or other device) connectable to a patient""s body from outside of said patient""s body or insertable into said blood vessel through said catheter.
Preferably information from said heart rate sensor is transferred to said central control unit enabling synchronization with said physiological conditions.
According to a fourth aspect of the present invention there is provided a method for performing biopsies and other diagnostic or therapeutic procedures comprising placing an invasive optical assembly apparatus on the distal end of a needle, inserting said optical assembly and needle into vasculature or other organs, and using said optical assembly to provide visual feedback of said biopsies and diagnostic or therapeutic procedures.
According to a fifth aspect of the present invention there is provided a method for viewing through blood in Situ comprising injecting a controlled amount of fluid into blood in the immediate region in front of an invasive optical assembly, temporarily changing the optical characteristics of the blood in said immediate region, and thereby improving visibility through said blood.
According to a sixth aspect of the present invention there is provided a method for viewing through blood in Situ comprising inject a controlled amount of fluid into blood in the immediate region in front of an invasive optical assembly, temporarily changing the reflectance of the liquid portion of said blood, and improving visibility through said blood.
Preferably said fluid is used to change the optical characteristics of blood in Situ to facilitate imaging through said blood, said fluid being a physiological fluid, such as saline, or a hypoosmolar fluid, such as 0.45% saline or 1/16 saline.
Preferably said fluid for use in changing the optical properties of blood in Situ to facilitate imaging through said blood, said fluid being a blood substitute which does not contain red blood cells and has homogenous optical characteristics.
Preferably said fluid is chosen to enable illumination to facilitate imaging through said blood and the environment in Situ with an IR illumination source, enabling a frequency shift so that a visible light sensor can be effectively used.
Preferably said fluid is chosen to be oxygen carrying, such as a blood substitute, to reduce the risk of hypoxia to the heart muscle.
According to a seventh aspect of the present invention there is provided a method for reconstructing images by interpolating image data along at least one of the longitudinal and axial axes of a flexible catheter with a distal end inserted into a blood vessel and thereby reaching remote places in the vasculature or other organs, based on image data from both said longitudinal and axial axes, comprising:
a. off-line image training initialization, and;
b. real-time image data interpolation.
Preferrably said off-line image training initialization comprises:
a. training image construction;
b. reconstruction of a lower resolution new image from said training image;
c. finding edge directions of said lower resolution image, and;
d. training a neural network to obtain a set of filters.
Preferably said tar image is clipped and rotated to obtain robust edges in each one of a plurality of directions.
A preferred embodiment executing local contrast enhancement following said image data interpolation.
Preferably said local contrast enhancement comprises:
a. calculating the average intensity of said real time image, yielding an intensity image;
b. generating a first image by correcting the intensity of said intensity image;
c. calculating a local contrast image;
d. generating a second image by enhancing said local contrast image, and;
e. summing said first image and said local contrast image to generate an output image.
Preferably said fist image is produced by modifying the intensity of said real time image using a lookup table.
A preferred embodiment comprises generating said second image by modifying the local contrast of said real time image using a lookup table.
Preferably said real-time data interpolation comprises:
a. finding edge directions of each pixel, and;
b. interpolating data using an appropriate direction filter from a set of direction filters.
A preferred embodiment comprises generating said set of direction filters in said off-line image training.